Blood groups ABO and grass-pollen hayfever.

The frequency distribution of the blood group phenotypes ABO was examined in retrospect in a selected group of 241 Patients with grass pollen hayfever. A relative deficiency in blood group O was found, with a shift toward an over-represented B-phenotype as compared to the general population. This shift appeared to be largely due to the contribution from the female patients with pollinosis. Comparison with literature data confirmed a lower frequency of the O-phenotype in atopic patients in general, irrespective of the specific sensitivities.